Conventionally, a sheet processing apparatus is known which executes a post processing such as a stapling processing on sheets loaded on a processing tray. In order to adjust deviation between the sheets loaded on the processing tray which are subjected to the post processing, the sheet processing apparatus includes a member for adjusting (horizontally aligning) the deviation in a width direction of the sheet and a member for adjusting (vertically aligning) the deviation in a direction orthogonal to the width direction of the sheet. Particularly, with respect to the deviation in the direction orthogonal to the width direction of the sheet, the deviation of the sheets loaded on the processing tray is aligned by using a vertical alignment member that rotates around an axis of rotation extending in the width direction of the sheet.